It is often desirable to tune mechanical systems to the specific operating conditions they are/will be subjected to in order to optimize their performance. Examples of such mechanical systems in which tuning can be beneficial are many, such as vehicle shock absorbers, natural and artificial skeletal joints, connections components within structures or devices, to name just a few. Conventionally, mechanical systems are tuned in a variety of ways.
For example, some structures are tuned during their design and engineering phase using a mathematical process known as structural dynamic modification (SDM). Typically, in an SDM simulation process an initial design is created and subjected to a modal analysis to create a modal model of the structure. This modal model, typically comprising frequency, damping and mode shape data for the structure, is used to determine the effects of changes in system characteristics due to physical changes made to the structure in achieving a response that fall within acceptable limits. This process of changing the mechanical system to suit response criteria may be referred to as “tuning ”. Once the SDM simulation process shows that the response of the mechanical system is acceptable, the actual system can be built. Relatedly, other simulations, such as force response simulation, can be performed to predict the response(s) of a mechanical system to one or more design forces applied to the system. As with SDM simulation, force response simulations are often used in an iterative manner to change the design of a system, i.e., “tune ” the system, until an acceptable response is achieved for the design forces. Likewise, once a desired response is achieved through simulation, the actual system can be built. Depending upon the nature of the mechanical system, once the system has been built from the design, the response of the actual system to an applied, known input force is measured to confirm that the simulations sufficiently predicted the behavior of the actual system. This type of tuning does not involve the monitoring of changes in the response of the system over time.
Whereas the tuning of some mechanical systems is accomplished during the design and engineering phase, in other cases existing mechanical systems are tuned using measured response data. For example, dynamically adjusting suspension dampers (shock absorbers) for automobiles utilize multiple sensors placed in various locations on the automobile to provide feedback information to a microprocessor that dynamically adjusts the damping rates of the dampers in response to the information from the sensors. In this scenario, information regarding the input loads to the suspension system is not collected. Only information relating to the response of the suspension system and, often, information regarding driver input, e.g., steering, throttle and braking information, is utilized in the algorithm for adjusting the damping rates.
In addition to tuning mechanical systems, it is often desirable to monitor the performance, or “health,” of mechanical systems over time. This is typically done in the context of large civil structures and expensive aircraft and spacecraft. Similar to conventional tuning of existing mechanical systems, performance monitoring systems typically utilize only measured response data.